We propose to continue the purification of a peptide (OMI) of about 2,000 molecular weight present in pig follicular fluid which inhibits the maturation of oocytes in vitro. We describe procedures for its isolation in pure form, and determination of its amino acid composition and sequence. The regulation of secretion of OMI from granulosa cells will be studied and a number of hormones (FSH, LH, androgens, estradiol, prolactin, prostaglandins) will be employed to determine which compounds might increase (or decrease) the secretion of OMI into culture media. After a pure compound has been isolated antibodies will be prepared and used to aid in the development of a radioimmunoassay for OMI, improve the purification, and study the physiological role of OMI. Additional efforts to understand the mechanism of action of OMI will be made by studying the ability of OMI fractions to inhibit the binding of FSH and LH to granulosa cells and to inhibit the FSH and LH mediated stimulation of accumulation of cyclic AMP and progesterone by these cells.